ROUX, WILHELM

Roux single-mindedly devoted his life to science. Even in his autobiography he gave only the scantiest details about his family and extrascientific activities. The obituaries and tributes by admirers fail to provide us with more.

Roux was the fourth child and only son of F. A. Wilhelm Ludwig Roux, a well-known university fencing master, and Clotilde Baumbach. The paternal side of the family stemmed from a Huguenot line that fled France after the revocation of the Edict of Nantes. Roux himself described his youth as being freudearm and explained that by inclination he remained aloof from most of his school comrades. Instead, possessing an early interest in science, he immersed himself “secretly” in Johann Müller’s Pouillet’s Lehrbuch der Physik und Meteorologie. At the age of fourteen he attended the Oberrealschule in Meiningen, where its director encouraged his scientific bent. The Franco-Prussian War interrupted his first year at the University of Jena. Upon his return from military service, and after additional preparatory studies, Roux matriculated in 1873 in the medical faculty. He attended the lectures of Preyer, Haeckel, and Gustav Schwalbe, and Rudolf Eucken’s seminar on Kant, an experience Roux always cherished. Two semesters in Berlin working under Virchow, a semester listening to Friedrich von Recklinghausen in Strasbourg, and a dissertation completed in 1878 under the supervision of Schwalbe completed Roux’s formal education. During the winter of 1877 he passed his state medical examinations.

Roux’s first employment was in Leipzig as an assistant at Franz Hofmann’s hygienic institute, a position which he later confessed taught him the value of exacting laboratory techniques. Relief came from the drudgery of analyses when in 1879 Carl Hasse invited him to his anatomical institute in Breslau (Wroclaw). Roux remained there for ten years (18791889), first as Dozent, then as associate professor, and finally, after April 1889, as director of his own Institut für Entwickelungsgeschichte. In August of 1889 Roux became professor of anatomy in Innsbruck but returned to Prussia in 1895 as director of the anatomical institute at the University of Halle, a position he held until April 1921. By the time of his retirement he had seen himself honored on many occasions as the founder of Entwicklungsmechanik. At Halle a prize had been established in his name for contributions in experimental embryology, and the University of Leipzig made him an honorary doctor at its tercentenary. Roux was a member of thirty-seven professional societies and an honorary member of the Deutsche Anatomische Gesellschaft and the American Society of Naturalists. At his death Roux was survived by his wife, Thusnelda Haertel, two sons, Erwin and Wilhelm, and a daughter, Irmgard.

Any attempt to evaluate Roux’s long and prolific scientific career is made difficult by the task of sifting the real achievements from the reams of proclamations and self-assertions. That Roux had a substantial impact upon his peers and upon contemporary embryology there can be little doubt, but it is equally clear that he was a ferocious propagandist for his own accomplishments.

Jena, where Roux studied and did his first research, was an exciting and intense place for an aspiring embryologist. Haeckel, at the height of his career, had just refashioned the zoological institute. While Roux was a student, Haeckel lectured on general zoology, vertebrate natural history, embryology, anthropology, and human histology. Roux attended some of these courses and confessed that he was influenced by Haeckel’s style and monistic philosophy; he insisted, however, that he never worked directly under Haeckel’s tutelage. The physiologist Preyer was closer to his own age. Roux knew him personally and must have been familiar with his many physiological experiments on developing chicks. Later Preyer’s Spezielle Physiologie des Embryo (1885) revealed the extent to which his physiological experiments had become oriented to the problems of development, if not differentiation. Roux’s own supervisor, Schwalbe, was an anatomist who had a lively concern for the mechanics of growth. It was Schwalbe who first directed Roux to the problem of relating form to function in the embryo.

Roux’s dissertation grew out of his studies on the form of branching blood vessels in muscle mesoderm. He developed a technique of injecting wax into the vessels, and upon dissolving the surrounding tissues, he was left with only a naked casting of the branches. His intent was to generalize the shapes and angles of vessel branching into rules of development. Thus, for example, Roux concluded that the axis of a tributary vessel lay on the plane which contained the longitudinal axis of the main vessel and the center of the ellipse formed by the juncture of both vessels. It is interesting to note that even at this early stage in his career Roux did not confine his generalizations to a descriptive equation. He’ drew a parallel between the vessel branches and the shape and direction of flowing water and thereupon arrived at a tentative conclusion that blood pressure had a bearing on the patterns of branching. By making an analogy between hydrodynamics and hemodynamics, Roux implied a search for a causal connection between function and form. It is also clear that this causal quest in the form of analogies came closer in spirit to the cellular mechanics exemplified in His’s celebrated Unsere Körperform und das physiologische Problem ihrer Entstehung (1874) than to the causal analysis exemplified in his later experimental embryology.

In his efforts to explain certain adaptive effects along the vessel walls, Roux developed a theory which he soon elaborated in a highly speculative treatise. Published shortly after Roux became a Privatdozent in Breslau, Der Kampf der Theile im Organismus (1881) offered a provocative challenge to biologists. Haeckel praised the work as an extension of his own ideas; Darwin remarked upon its importance; but Roux’s own mentor, Schwalbe, warned him never again to publish such a “philosophical” book.

In essence, Roux envisioned a natural selection at a microscopical level. As were most of his contemporaries, particularly Haeckel, Roux was convinced that Darwin’s account of natural selection failed to explain the patent functional harmony of an organism or the myriad correlative changes that must occur in each phylogenetic step. Moreover, as did Haeckel, Roux insisted upon invoking only a mechanistic cause for the apparent purposefulness of body parts and the implied directionalism in evolution. Now guided by his embryological research, Roux argued that a struggle for existence must take place on the cellular and molecular level, that those molecules and cells that assimilated material and grew most rapidly produced the most offspring. Roux considered that nutritive and functional stimuli provided the microenvironmental circumstances for the struggle. If persistent, these microeffects became grossly manifested as visible variations. These variations were the grist, he argued, for the mill of Darwinian selection.

Roux thought that he fully understood the implicit statistical nature of Darwin’s theory and that he understood natural selection as a creative as well as destructive force. He underestimated the selective value of small variations on the organismic level, and he confounded physiological changes in development with the genetic makeup of an individual. Such a confusion was commonplace with the generation that followed Darwin’s lead in accepting the inheritance of acquired characteristics. Only after biologists had made an explicit distinction between the genotype and the phenotype would such physiological explanations of evolution become obsolete. Although later in his career Roux progressed toward such a distinction, lie never fully recognized its implication for his theory of a micronatural selection or a “Kampf der Theile.” Throughout his life he continued to insist on the close bond between intracellular and intraorganismic selection.

Roux’s emphasis on the mechanism of functional adaptation did lead, however, to an examination of the physical stresses and strains that caused bones, cartilage, and tendons to adapt to malformations, diseases, and accidents. Roux’s own initial discussion of these effects appeared between 1883 and 1885 in three “Beiträge zur Morphologic der ’functionellen Anpassung’ “; he contributed extensively throughout his life to the subject, and both anatomists and orthopedists, found great value in Roux’s theoretical and descriptive accounts. There is little doubt that as an explanatory concept “functional adaptation”— development induced by nutrition and functional stimuli—always constituted an important part of Roux’s understanding of the development of form. It is necessary to point out again that this side of Roux’s research was not experimental in design.

If Roux had found at Jena congenial philosophical and methodological commitments among his major professors, at Hasse’s institute in Breslau he found two young contemporaries who were imbued with the same analytical spirit. Gustav Born, a student of the physiologists Rudolf Heidenhain and Eduard Pflüger, was prosector at the time of Roux’s arrival. His many embryological experiments were closely related to Roux’s own interests, and when the latter set up his own Institut für Entwickelungsgeschichte, Born joined him as an associate professor. Hans Strasser, a Swiss by birth, was the first assistant. He had a special aptitude for mathematics, and his research interests involved the mechanics of locomotion. Hasse himself represented the mid-century tradition of microscopical anatomy; but according to Roux, lie did not discourage the mechanical and causal orientation of his younger colleagues.

It was in these congenial surroundings that Roux embarked upon a new course in experimental embryology. The transition from a descriptive analysis of observed effects to an experimental sorting of causative factors took two steps to reach fruition. The first published indication of a change, a pamphlet entitled Ueber die Zeit der Bestimmung tier Hauptrichningen der Froschembryo, appeared in early June 1883. In this monograph Roux examined the earliest structures of amphibian development in order to determine whether the medial axis and the head-tail orientation bore any relation to the early cleavage patterns. After immobilizing the fertilized eggs with pins, he marked the position and direction of the planes of the first two segmentations. As development continued and as the medial axis and orientation became established, Roux found that they correlated with early cleavage. Here was an indication that the structure became determined at the very first stages of development; but, as yet, Roux had only described the sequence of events, not isolated their causes.

On 10 June 1883, just prior to the appearance of Roux’s work, Pflüger published a paper on the influence of gravitation on cleavage. He, too, scrutinized the position and orientation of the primary axis of the fertilized egg, the plane of cleavage, and the medial axis of the embryo. Instead of just describing the relationship as Roux did, Pflüger went on to rotate the fertilized egg before first, second, and third cleavages, thus creating new relationships between the egg and the force of gravity. His manipulations of the egg led him to believe that the cleavage planes were independent of the primary axis and that third cleavage was always perpendicular to the force of gravity. Pflüger could then argue that gravitation played a determinate role in the processes of differentiation. The internal structure of the fertilized egg, Pflüger continued, was unimportant for the future embryonic form: “The reason the same structure always arises from a germ is because it is always subjected to the same external circumstances.”1 This was a defiant challenge from a physiologist, a challenge that could be answered only with counterexperiments.

A number of embryologists, among them Roux and Born, were quick to respond. Roux devised a vertical wheel upon which he could rotate tin containers of developing eggs. By varying the rate of rotation and the location of his samples along the radius of the wheel, he reasoned that he could counterbalance or even replace the gravitational effects by a centrifugal force. No matter how Roux arranged the interaction between the two forces, all the eggs cleaved normally and continued to develop. It was clear that neither force could rank as the determinative agent; and thus, in rebuttal to Pflüger, Roux claimed that the differentiating cause must be internal to the egg. More important than these conclusions was the fact that Roux, in following Pflüger’s example, had isolated and tested a particular factor of development. His manipulations had led him beyond a descriptive account to a causal analysis and experimental embryology.

Pursuing his interest in the determining influences of early cleavage, Roux investigated the penetration and copulation paths of the male pronucleus, the effects of mechanical pressure on the fertilized egg, and the relation between the gray crescent and medial axis. His Anstichversuche, or injury experiments, constituted the most interesting line of new work. Roux had pierced blastomeres with needles as early as 1882, that is, prior to Pflüger’s and his own rotation experiments, but at that time he was concerned with tracing the movement of the resulting protoplasmic exovates. Only after 1883 did his experiments become exemplars of causal analysis.

Roux had by this time embarked upon a program to isolate the causal factors of early development. His own words describe vividly his image of the physical manipulation he performed:

I was fully conscious of the crudeness of this attack on the secret workshop of all the forces of life and compared this act to the insertion of a bomb into a newly founded factory, perhaps into a textile work, with the undertaken purpose of making a conclusion about the factory’s inner organization from the change of production and its further development after the prepared destruction.2

Wherever Roux threw his “bomb” he created developmental distortions. It is apparent, given the number of embryonic stages he attacked and the great diversity of results he obtained, that only with the aid of some unifying principle could he hope to organize these experiments into a meaningful pattern. In his first major paper devoted to these efforts, Roux attempted to do just that.

Roux found his way through the confusion of teratological details of his experiments by attending to the interaction between the nucleus and cytoplasm and asking questions about the relative value of each in the process of differentiation. Since the late 1870’s the nucleus had become a particular object of cytological scrutiny; so Roux’s focus was an entirely befitting one. By isolating a portion of the cytoplasm in exovates which extruded from the point of injury, Roux placed himself in a unique position to demonstrate whether cytoplasm developed without nuclear effects and whether the body of the embryo could sustain a substantial loss of cytoplasm without abnormal development. The manner in which Roux generalized such concerns fashioned a useful tool for his later experiments; in short, he conceived of the entire course of development as moments of independent and dependent differentiation (Selbstdifferenzierung and differenzierende Correlation, later abhängige Differenzierung). His puncturing needle gave Roux the opportunity to sort out cause and effect by isolating individual factors.

The value of his experimental technique and of the organizing concepts of dependent and independent differentiation attained full fruition only with Roux’s celebrated half-embryo paper of 1888. Beginning in the spring of 1887, Roux punctured fertilized frog eggs with a heated needle. His intent was obvious—the destruction of nuclei during early cleavage. Roux found that he could destroy any combination of nuclei before the third cleavage.

The results were much more dramatic than his earlier Anstichversuche had led him to anticipate. Upon preserving and staining his specimens at gastrulation, Roux found that he had produced halfembryos: semiblastulae, and semigastrulae with clearly identifiable single neural folds, and anterior and posterior semigastrulae. It seemed to him that the undisturbed blastomeres had continued to develop as though nothing had happened. Roux inferred that development was “a mosaic of at least four vertical pieces each developing substantially independently.”3 Roux also noted that the damaged half occasionally became reorganized at a later stage as nuclei from the developing half migrated into the cytoplasm of the disturbed blastomere—a “postgeneration,” as he called it. Both phenomena, the normal development of the undamaged blastomeres and the regeneration of the pierced blastomeres, demonstrated the interplay between Roux’s basic factors of independent and dependent differentiation. His experimental technique had isolated a formative action in the nucleus and had seemingly shown that the nucleus of each blastomere contained both the necessary and sufficient developmental components to direct a specific independent line of differentiation.

Although this mosaic pattern of development in the frog was shown in 1910 to be an inaccurate description of true amphibian development, it accorded well with a highly speculative suggestion made by Roux himself as early as 1883. At that time Roux became interested in Strasburger’s and Flemming’s work on karyokinetic figures. Obviously, Roux rationalized, such a complex and indirect division of the nucleus must serve some functional purpose; here perhaps was a mechanism for dividing the nucleus into two qualitatively unequal halves and for segregating these differences to the daughter blastomeres. During this speculative foray, Roux also indicated that he had become wedded to a belief that the nucleus itself was composed of a complex of macromolecules or hereditary particles; it was these units, he suggested, which were “purposefully” parceled out during the mitotic divisions of development. The 1888 “half-embryo” work, with its dramatic demonstration on the somatic level of independent differentiation of the first four blastomeres, corroborated perfectly with the notion of unequal nuclear division. Roux forgot the fanciful overtones of his 1883 suggestion and began to speak of mosaic development as a germinal phenomenon as well as a description of somatic events.

In 1893, in a monograph on mosaic development, Roux underscored the connection he had inferred between the events of early cleavage and the patterns of nuclear division. There is no doubt that in this general statement Roux saw inheritance and development as opposite sides of the same coin. The material that passed from generation to generation had to be so constituted as to initiate and carry on nearly identical processes of embryogenesis. At the same time the somatic cells, those resultants of differentiation, must contain very different genetic arrangements. Roux felt the paradox could only be resolved by accepting an isolated germinal track and his earlier suggestion of qualitatively unequal nuclear division during development. Moreover, in accepting the proposition that there existed hereditary particles, Roux insisted that he was not resurrecting the discredited theory of preformation; after all, he still recognized a correlative interaction between cells at most stages of development and during the process of regeneration. Only in 1902, after Theodor Boveri had marshaled strong evidence against qualitative nuclear division, did Roux relinquish his belief that a mosaic development was directly caused by the mechanics of mitotic division. The concept of a mosaic development was restored to a description of somatic events. After Boveri’s demonstration Roux reasoned that the cytoplasm and the nucleus must continually interact with one another during development. His primary distinction between independent and dependent differentiation, however, remained a basic dichotomy and organizing theme for subsequent embryological research.

It was claimed that Roux was a propagandist as well as an investigator. The banner under which he marched was Entwicklungsmechanik, and the domains he defended were experimentalism and mechanism. Roux maintained a parochial view of the advent of experimentalism in embryology. His concern to establish priority over Pflüger when they simultaneously published experimental work on the determination of the longitudinal axis in amphibians was a typical reaction. On a number of occasions Roux drew up a four-tier hierachy of scientific method in an effort to distinguish his own accomplishments from those of his contemporaries and predecessors. He explained that the (1) descriptive and (2) comparative methods were the most primitive and least informative about the causes of development. The (3) descriptive experiment, Roux claimed, was characteristic of the endeavors of His, Rauber, and Balfour, all of whom had searched for causes and even on occasion performed laboratory manipulations. Their experiments, however, were not systematic and were so constructed as to reveal only analogies between mechanical and embryonic phenomena. Roux maintained that only (4) a causal analysis, that combination of mental and laboratory isolation and manipulation of biological factors, gave the scientist a certainty about the causes of development. He contended that he alone had first moved beyond casual manipulations to a causal analysis of development; this was the core of his Entwicklungsmechanik.

His insistence was, of course, absurd, for it overlooked the work of his contemporaries Hertwig, Pflüger, and Born, to say nothing of the older tradition of experimental teratology in France. Nevertheless, Roux’s assertions had some basis. He had dramatized experimentation on the embryo in a way that his peers had not, and in a unique manner he had made explicit that a true experiment was not just a manipulation of the egg but included a mental dissection of development into a number of hypothesized factors. In this respect his analysis of development into dependent and independent factors promoted a causal understanding. Roux’s model for experimental embryology was physiology, and it was befitting that the physiologist Rudolf Heidenhain suggested to Roux the term Entwicklungsmechanik for his program of research.

Entwicklungsmechanik denoted more than a method of research; Roux made it clear that he was ascribing a mechanistic interpretation to the embryological events he discovered. It was not a simple and crude mechanism which read into every vital phenomenon the direct action of matter in motion. Instead, it entailed a commitment to the forces and matter legitimized by physicists and chemists and accepted these as the appropriate and sole ontological entities to be employed in a causal understanding of life. Despite such a metaphysical commitment, Roux recognized that biologists might never succeed in the task of explaining vital activities in physical and chemical terms. This nevertheless was the challenge and the only legitimate pursuit for the biologist.

Finally, Entwicklungsmechanik was a declared program of research. Roux recognized that its methods were akin to physiology yet the object was the explanation of form; it was therefore a new approach to a traditional morphological problem. In a revealing passage, Roux explained that he employed the term because no matter how experimentally inclined his students might be, they would never be eligible for academic chairs in physiology. The appellation helped them maintain a claim on positions in anatomy.

To further his program, Roux promoted a number of publications. His Archiv für Entwicklungsmechanik der Organismen (after his death retitled Roux Archiv für Entwicklungsmechanik) was founded in 1894 and continues to be published. For many years it was the most prestigious journal in experimental embryology and served as the model for its American counterpart, Journal of Experimental Zoology. Roux founded two monograph series, in 1905 and 1909. He initiated the first of these with his Entwicklungsmechanik, ein neuer Zweig der biologischen Wissenschaft, which came closer than any of his other works to serving as a textbook for his program. A dictionary, Terminologie der Entwicklungsmechanik der Tiere und Pflanzen, compiled in collaboration with two botanists, Correns and Küster, and an anatomist, Fischel, presented a valuable compendium of definitions and historical notes for the general area of experimental morphology. Roux himself is cited as the originator or discoverer of so many of the entries, however, that the work today is little more than a mirror of a past age, reflecting the tight and egocentric hold Roux kept on his program. A Festschrift, published on his seventieth birthday, contained both accolades and thoughtful papers devoted to examining Roux’s impact on other fields. Its collective message left the impression that many leading biologists identified with a tradition headed by Roux. Roux produced in his autobiography a long list of biologists (forty-four Germans, seventeen Austrians, and twenty-three Americans, among others) who he claimed were all representatives of Entwicklungsmechanik. Despite the implications, they can hardly be considered to have constituted a school of Roux students and devotees, for the list contains nearly all the important embryologists and cytologists of the day.

Experimental embryology was hardly the invention of Roux. He excelled in it at a time when it made dramatic strides; he made substantial contributions to theories of development and inheritance; he proselytized for and philosophized about it; and he produced the journals and terminology for its dissemination. To the degree that he performed these tasks more zealously than his contemporaries, he was the titular sire of modern experimental embryology.

3. Wilhelm Roux, “On the Artificial Production of Half-Enmbryos by the Destruction of One of the First Two Blastomeres…,” Benjamin H. Willier and Jane Oppenheimer, eds., Foundations of Experimental Embryology, p. 36.

Roux, Wilhelm

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

Wilhelm Roux (vĬl´hĕlm rōō), 1850–1924, German anatomist, a founder of experimental embryology. He was a pupil of Ernst Haeckel and a professor (1895–1921) at the Univ. of Halle. In his studies of the relationship of embryology to evolution he developed specialized research techniques that he called
"developmental mechanics,"
and in 1894 he founded as its organ the Archiv für Entwicklungsmechanik.

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